There is a known technology for creating, from stereo images imaged by multiple imaging devices, stereoscopic images for displaying stereoscopic video images. The stereo images mentioned here indicate, for example, multiple images having predetermined parallax. Examples of these imaging devices include digital cameras, cameras mounted on mobile terminals, cameras mounted on personal computers (PC), or the like.
Furthermore, there is also a known technology for creating stereoscopic images, by using images imaged by a single imaging device and by using images obtained by moving, by the predetermined parallax, objects in the images that are acquired by the single imaging device with a simple structure when compared with a case in which multiple imaging devices are used.
Furthermore, there is also a known technology for switching stereoscopic video images and two-dimensional video images in accordance with the preferences of a user, such as a member of an audience.
Patent Document 1: Japanese Laid-open Patent Publication No. 2001-054141
Patent Document 2: Japanese Laid-open Patent Publication No. 2005-124200
Patent Document 3: Japanese Laid-open Patent Publication No. 08-111876
However, with the conventional technologies described above, there is a problem in that a burden is placed on the user. Specifically, with the conventional technologies, a user switches a stereoscopic video image to a two-dimensional video image by an operation. The stereoscopic video image is switched to the two-dimensional video image when, for example, the user feels tired. More specifically, because the user conceives a stereoscopic video image from a visually identified video image and composites the stereoscopic video image, when viewing the stereoscopic video image, the level of tiredness is large when compared with a case of viewing two-dimensional video images. Accordingly, in some cases, the user switches the stereoscopic video image to the two-dimensional video image that are less tiring to view. However, a burden has already been placed on the user at the time when the user feels tired.
The focal length of the eye of the user with respect to a stereoscopic video image is different from that with respect to a two-dimensional video image. Accordingly, the focal length varies when switching the stereoscopic video image to the two-dimensional video image, which is one of the burdens placed on a user.